(a) Field of the Invention
The present invention relates to a dielectric ceramic composition and, more particularly, it relates to a dielectric ceramic composition which can be sintered at low temperature, whose dielectric constant has a small changing ratio relative to temperature, and which is most suitable for laminated substrates and chip capacitors.
(b) Prior Art
Ceramic compositions having barium titanate (BaTiO.sub.3) as their main component have been widely used for ceramic dielectrics of high dielectric constant.
Such compositions need a high temperature of 1,300.degree.-1,400.degree. C. as their sintering temperature, and the ceramic thus obtained shows a relative dielectric constant of 1,500 at room temperature and a relative dielectric constant of 10,000 at a Curie point of 120.degree. C. The dielectric constant of this ceramic also shows a large changing ratio of several times room temperature. Due to the high sintering temperature of 1,300.degree.-1,400.degree. C. and, particularly in the case of forming laminated capacitors, therefore, metal whose main component is expensive platinum, palladium or the like suitable for this sintering temperature must be used as the inner electrodes. A ceramic composition which can be sintered at low temperature, particularly lower than 1,000.degree. C., which has a relative dielectric constant larger than 1,500, and whose dielectric constant has a small changing ratio relative to temperature is needed.